Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON):

Solution:
from collections import deque
h, w = map(int, raw_input().split())
maze = [raw_input() for _ in xrange(h)]
visited = [[False] * w for _ in xrange(h)]
que = deque([(0, 0, 0)])  # prepare for bfs.
dx, dy = (0, 1, 0, -1), (1, 0, -1, 0)
dis = flag = False
while que:
    x, y, d = que.popleft()
    if (x, y) == (h - 1, w - 1):
        dis, flag = d, True
        break
    for i in xrange(4):
        nx, ny = x + dx[i], y + dy[i]
        if 0 <= nx < h and 0 <= ny < w:
            if not visited[nx][ny] and maze[nx][ny] == '.':
                que.append((nx, ny, d + 1))
                visited[nx][ny] = True
print h * w - dis - 1 - sum([_.count('#') for _ in maze]) if flag else -1